The semiconductor integrated circuits (IC) industry has experienced exponential growth. With such growth, technological advances in IC materials and designs have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. As a result, more complex circuits require more sophisticated manufacturing/processing methods of etching, deposition, and so on. A variety of methods are used in the semiconductor manufacturing industry to deposit materials onto surfaces. One of the most widely used methods is chemical vapor deposition (“CVD”), in which atoms or molecules are contained in a vapor deposit on a surface in order to form a film. CVD allows for the growth of films on device surface areas, including “epitaxial” films comprised of a crystalline silicon-containing material.
In some applications it may be desirable to achieve uniform or “blanket” deposition of epitaxial growth over mixed surfaces, such as insulating and semiconductor surfaces, while in other applications it is desirable to achieve “selective” deposition only over selected surfaces. Such selective deposition allows for growth in particular regions of an underlying structure by taking advantage of differential nucleation during deposition on different materials.
Selective deposition generally involves simultaneous deposition and etching of an epitaxial material. During a typical selective deposition process, a precursor of choice may be introduced that has a tendency to nucleate and grow more rapidly on one surface (e.g., a semiconductor surface) and less rapidly on another surface (e.g., an oxide surface). An etchant is added to the deposition process, which has a greater effect upon the poorly nucleating film as compared to the rapidly nucleating film, therefore allowing growth only on specified surface areas. The relative selectivity of a selective deposition process is tunable by adjusting factors that affect the deposition rate (for example, precursor flow rate, temperature and pressure) and the rate of etching (for example, etchant flow rate, temperature and pressure). By precise tuning, epitaxial growth may be achieved with complete (e.g., zero growth on insulators and net growth, albeit slow, on single crystal windows) or partial (e.g., net growth on insulators and single crystal windows, with the net growth on the insulator being of lesser thickness than on the single crystal windows) selectivity on desired surfaces. However, while known processes often result in selective epitaxial growth, such growth is often of poor quality. Measures to improve epitaxial growth are continuously being sought.